Method of changing the composition of iron and steel.



B. FORD. METHOD OP CHANGING THE COMPOSITION 0I`I IRON AND STEEL.

APPLICATION FILEI) JAN. 12, 1909.

Patented May 20, 1913.

W/T/VESSES:

BRUCE FORD, OF PHILADELPHIA, PENNSYLVANIA.

METHOD OF CHANGING THE COMPOSITION OF IRON AND STEEL.

Specification of Letters Patent.

Patented May 20, 1913.

Application led January f2, 1909. Serial No. 471,873.

T 0 all whom it may concern:

Be it known that I, BRUCE FORD, a citizen of the United States, and a resident of Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in the Method of Changing the Composition. of Iron and Steel, of which the following 1s a specification. v

The composition of iron and steel may be changed to a substantial depth or throughout the mass by cementation or de-cementation, but the processes heretofore employed for this purpose required for their completion a eat la se of time, measurable by days. ase hard a mere surface skin has been accomplished by electrically or otherwise heating the metal to or below its welding temperature and whilehot rubbing the surface with a suitable steelifying material, such as potassium cyanid.` This can bequickly accomplished, but itresults inthe production of a mere superficial skin.

The principal object of the present inven' tion is to provide an expeditious method for accurately controlling or changing the carbonl contents"and-.hardening constituents of iron and steel throughout 'the mass or to a substantial-' ydepth-To this end I heat the "metal to above its weldingheat and even melt it (though the ymelting. process'forms the subjeCt-matterof my application serially numbered -255,359 dated April 13th, 1905) while in contact with a medium adapted to operate absorptively by contact, or by cementation or de-cementation.

My process is based upon the marked rapidity with which the change in composition occurs fora comparatively small elevation of the temperature of thev metalv above the temperaturev heretofore employed in cementation or de-cementation processes, which temperature was below or approached the temperature ofthe welding point of the metal. Icontemplate practising the process at a temperaturel above the temperature of the welding point of the metal, even up to or beyond its meltinfr point7 the lat-ter being described and claimed in my application above referred to.

The drawings illustrate one, but not the only, type ofapparatus which may be used for the practice of the process of the invention, and inthem Figure l, is a sectional f view partly diagrammatic, illustrating such ening or the carburizing of A apparatus, and Figs. 2 and 3, are detail views illustrating modifications of the contact.

To practise the process of the invention the metal is exposed to or immersed in a suitable medium and while permitted to remain or stay therein, is heated in such a way that p. the temperature of its body or mass is raised above its Welding point. The metal remains exposed to these conditions until the composition of the whole of it is changed or until its composition is changed to the desired depth, which is a matter of, comparatively, a very short time, measurable in minutes or hours as distinguished from hours or days or even weeks (according to the heat applied and depth required) in the cementation and de -cementation processes. The temperatureto which the body or mass of metal is heated.

can be accurately controlled and regulatedl.

during the entire period of time in which the metal remains immersed in or exposed .to the medium by the use of electric heat.

The medium may be of a carbonizing nature,

in which case the effect is to cause the iron to absorb or take on carbon1 thus producingv the well known changes in 1t which are due to the addition of carbon; on the other hand the medium may be of a de-carbonizing char- 85 acter,in which case it deprives the iron'or steel of carbon, thus producing in it corresponding changes.

For thesake of a further description, an explanation of the method as practised in the apparatus shown will now be given.

A, is a receptacle as of cast iron preferably fitted with a removable Vcover B. Conductor bars C and C1 lead into the receptacle A, but are insulated therefrom by the bushings D. Within the receptacle is the medium E, which may be either gas, vapor, liquid, or a granular or powdered mass.

F, F1, are contact pieces for the conductors C, C1 and between these is mounted and clamped the iron or steel G to be treated. A panel H, of transparent substancegsuch as glass, may for convenience, be put in the wall or cover of the receptacle and through this the progress of the process can be inspected. If the medium E is a gas or vapor it may be allowed to circulate by means of the inlet and out-let pipes K, K1. The source of power L, is in the case shown, an alternating current generator connected to a primary coil M, of a transformer N. The secondary coil of the transformer is formed by the conductors C, C1. The conductors C, C1, may be kept cool as by a circulation of water through them by means of the tubes O and O1. The iron Or steel to be treated is clamped across the contacts F, Fl and sufiicient current is turned on and con- Y trolled by means of the controller R, in the .under treatment.

primary circuit to heat the mass or body of the metal G, above its welding tempera-ture, whereupon it rapidly absorbs Or gives up carbon or other hardening constituents from or tO the medium according to its nature and in the manner described. Obviouslv the relength of the metal kto be treated there is required from two to five Volts, according tothe shape'of its cross-section and the capacity of the medium for taking away heat, but at any rate the current must be sufficient to heat the metal above its welding point andas its temperature is further increased the change in composition Occurs more rapidly.

. As an illustration of a carbonizingme- :j 1- dium reference may be made to the fumes of gasolene, some appropriate form of cyanogen, ground carbon, lamp black, bone black.

Orthe like, or a mixture of these or some of these; and as an illustration of a de- -=--1oarbonizi11g medium reference may be made Of powdered haematite and the like. lVhile reference has been made to adding carbon to iron or steel, it is obvious that by the present method other substances can be aradded, for example, the medium may constances whic tain manganese or silicon in some appropriate form Or in fact any of those subare availed Of in the treatment Of iron and steel. By the described inet-bod it is possible to first form articles into the required shape and to then treat them; the time required. for treatment is exceedingly short, being a matter of minutes rather than hours, as in the old process Of cementation.

There is interposed in the circuit high resistance at or near the ends of the parts tO be treated, the purpose of this is to compensate for the heat conducted away by the contact portions F, F1, and thus insure the uniform heating of the piece or mass throughout its length. This can be accomplished by reducing the cross-sectional area of the ends Of the piece, as at g. The ends and F5 is made small as at h, and therefore Of high resistance.

What I claim is: A 1. In the process of changing the composition of iron and steel by electrically heating it between contacts and in the presence of a suitable medium, that improvement which consists in increasing the electrical resistance of the metal at or near the cOnl tacts to provide heat to compensate for heat conducted away by the contacts- 2. In the art of changing the composition.' of iron and steel byv-interposing in `ari-,85 electric circuit in the presence of a suit-able f medium, that improvement-which consists in interposing in the circuit resistance at orf` near the ends of the partto bektreated higher y` than the resistanceof thev` rest olf-the circuit.;

3. In the process of changing 'thejcomposition Of iron and steel by electrically heating .3: it between contacts and'in the presence-(oa 4 suitable medium, that improvementyvhich. consists in increasing -theelectrical 'resist- A ance of the circuit 'at or vnear the contacts ,t0n

provide heat to compensateggfor heatconducted awayl by the contacts. il A 4. In theprocess*Ofgelectricallyheating 5"' Object between ,':contactsz-that improvement which consists infheating-f-theobject `luniformly byincreasing the' electricalfresist'- ance Of the circuitat or near the contactsl f,

to provide heat to compensate for heat con.- ducted away by both contacts. l. I

5. In the process of electrically heating anv object between contacts that improvement which consists in reducing 'the cross-sectional area of the` ends ,of` the body and thereby increasing the electrical resistance of the circuit at or near bothcontacts to pro-- vide heat to compensate for heat conducted away by the contacts. .1 1 g In testimonywhereof I--have lhereunto signed my name'.

In the presence of- GEO. M. HOWARD, LEONARD H. WORNE.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents, Washington, D. C.

BRUCE: FORD. y i 

